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Peter
Vail: The sedimentary time master
Like
many geologists in the oil industry during the 1960s, Peter Vail spent much
of his time studying sedimentary rocks in the subsurface that were once part
of ancient ocean basins for clues to their history, composition and relative
ages. Particularly in industry, this stratigraphic work relies heavily on seismic
data to help interpret and identify prospective hydrocarbon traps.
Oil companies in the early 1960s used seismic reflection data as a tool for
defining regional stratigraphic and structural subsurface relationships. But
their interpretation did not always work. Although a well would find sand in
one spot, another well following the same amplitude of the seismic reflection
would encounter silt or shale. Vail, however, found that the seismic reflections
were not recording a difference in lithology, so much as they were recording
different depositional histories in time. A layer that began as sand in one
spot and shale in another would share the same reflection signal — following
a geologic timeline.
Photo of Peter Vail courtesy
of EGI.
This new interpretation meant a drastic change from the business
as usual method, and many in the field opposed Vail when he first began presenting
his findings. “One senior geologist accused me of proposing that the reflections
were bouncing off the backs of fossils,” he said in a speech to accept
the Sidney Powers Memorial Award, given to him during the annual meeting of
the American Association of Petroleum Geologists (AAPG) in Salt Lake City. “Another
suggested that I was telling him that what he was teaching his students was
wrong.” Time and experience prevailed and now Vail’s concept is well
accepted.
“[Vail] has made major contributions to the understanding of earth science
and is very deserving of AAPG’s highest award,” says AAPG President
Dan Smith. At the AAPG ceremony, a long time friend and former Exxon colleague
Robert Mitchum, explained in a speech that, “When Peter Vail introduced
the concepts and applications of sequence stratigraphy, the effects on stratigraphic
geology and seismic interpretation were comparable to that of plate tectonics
on structural geology.”
Vail began his industry career as a research geologist with the Carter Oil Company,
a predecessor of ExxonMobil Upstream Research, in 1956. That same year he obtained
his Ph.D. in geology from Northwestern University and married his wife Carolyn.
While at Northwestern he had studied under Laurence Sloss, who in the 1950s,
was establishing a theory of continent-wide sequences. Vail took this idea of
sequences in the rock record to Exxon and at first began working with colleagues
identifying and publishing reports showing correlative patterns using well-log
marker horizons. When a colleague indicated that seismic data also recorded
these patterns, Vail switched gears to the geophysics section at Exxon, “against
the advice of my supervisors,” he told AAPG Explorer. There, with the help
of colleagues, he developed his concept of sequence stratigraphy and soon tested
it in the field.
In 1977, Vail and his team published in AAPG Memoir 26 examples of seismic reflections
that showed a high-amplitude signal off of a top layer of sand that continued
along time-synchronous sedimentary layers or bedding surfaces rather than following
the sand straight across. Vail soon went on to explain basin-wide stratigraphy
patterns resulting from changes in sea-level rise.
“As I was studying seismic sections, I noticed a pattern in the sequences
that onlapped [or overlapped at] the edges of the basin. I dated it with paleontology
and found similar ages and made charts and interpreted it as eustatic sea-level
and that idea is still being debated,” Vail says. Mitchum in his award
ceremony speech added that, “Pete’s ideas on the unifying paradigm
of eustatic cycles are probably as close to an original concept as most of us
are privileged to see.”
In 1986, Rice University appointed Vail as its W. Maurice Ewing Professor of
Oceanography. He retired from Exxon and began his academic career, while still
pursuing his ideas on basin-wide sequence stratigraphy and sea level effects.
In 1992 and 1993, he took a sabbatical in Paris where he worked to include European
basins in his study. The sabbatical, however, almost turned deadly when Vail
suffered a fall that ultimately left him paralyzed on the left side of his body.
Vail returned to Rice University where he continued to teach using a wheelchair
and later only a cane. “I still have the cane,” he says. He became
emeritus professor at Rice in 2001. The university and Exxon celebrated
Vail’s retirement with a kick-off party called the Vail Fest Symposium
that lasted for three days in March 2002 and featured talks from students and
colleagues. At the urging of his sons, Vail is now back in the oil industry.
As he explained to the AAPG audience in Salt Lake City, “I received many
wonderful compliments so my kids responded by saying, ‘If you’re so
smart why don’t you find us some oil?’ That sounded good to me, so
besides consulting I decided to invest in some oil and gas wells.”
Christina Reed
